Effects of ondansetron on electrically evoked contraction in rat stomach fundus: possible involvement of 5-HT2B receptors.
This study examined the effects of ondansetron, an antagonist of the 5-hydroxytryptamine (5-HT3) receptor without 5-HT4 receptor agonistic activity. on electrically evoked contractions and acetylcholine release in rat stomach fundus strips. Ondansetron (10(-8)-10(-4) M) produced a concentration-dependent increase in the magnitude of the electrically evoked contraction, while it inhibited the release of acetylcholine induced by electrical field stimulation. The stimulatory effect of ondansetron (10(-6) M) on electrically evoked contractions was antagonized by yohimbine, a 5-HT2B receptor antagonist, but not by SDZ 205-557 (2-methoxy-4-amino-5-chloro-benzoic acid 2-[diethylamino] ethyl ester), a 5-HT4 receptor antagonist. In the presence of tetrodotoxin, ondansetron (10(-7)-10(-5) M) enhanced the contractions induced by acetylcholine. This stimulatory effect of ondansetron on acetylcholine-induced contractions was antagonized by yohimbine. These data suggest that ondansetron potentiates the contractile response to acetylcholine in the rat stomach fundus through the activation of 5-HT2B receptors.
Amemiya
N
N
Department of Pharmacology, School of Medicine, Sapporo Medical University, Japan.
Hatta
S
S
Ohshika
H
H
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D004558:Electric Stimulation; D005748:Gastric Fundus / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D006859:Hydrogen / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D017294:Ondansetron / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism
D014151:Anti-Anxiety Agents; D011985:Receptors, Serotonin; D017294:Ondansetron; D006859:Hydrogen; D000109:Acetylcholine